8.2 g of 7-cyanooctanoic acid dicyclohexylamine salt are added to a mixture of 26 cm3 of a molar solution of sodium hydrogen sulphate and 60 cm3 of diethyl ether. The mixture is stirred for 15 minutes at 20° C. and the organic phase is then separated. The latter is dried over magnesium sulphate and filtered and the solvent is evaporated off under reduced pressure. The residue is treated with 13.2 g of thionyl chloride and heated to 50° C. for 3 hours. The mixture is concentrated under reduced pressure. The residual oil is dissolved in 5 cm3 of dichloromethane, and the solution obtained is added to a suspension, stirred and cooled at 5° C. of 7 g of 2-amino-1,2-bis(4-chlorophenyl)ethanone hydrochloride in 25 cm3 of dichloromethane containing 4.4 g of pyridine. After treatment, the product obtained is chromatographed on a column 2.8 cm in diameter containing 140 g of silica gel (50 to 200μ). The column is eluted with 1 liter of diisopropyl ether and then with 2.5 liters of a diisopropyl ether/ethyl acetate (90:10 by volume) mixture, collecting 250 cm3 fractions. The fractions from the last eluent mixture are concentrated to dryness under reduced pressure (0.2 kPa). 7.6 g (80%) of (RS)-1,2-bis(4-chlorophenyl)-2-(7-cyanooctanamido)ethanone are obtained in the form of a yellowish oil, which is used directly in the subsequent reaction.
